1. Field of the Invention
The present invention relates to epoxy resin compositions which are suitable for use as molding materials, powder coating materials, encapsulators for semiconductors and the like.
2. Description of the Prior Art
Epoxy resin composition comprising epoxy resins and inorganic fillers have better characteristics, e.g. moldability, adhesiveness, electric characteristics, mechanical characteristics, moisture proofness and the like, than other thermosetting resins. Accordingly, epoxy resin compositions have wide utilities as various molding materials, powder coating materials and electric insulating materials, particularly as encapsulators for semiconductors.
However, most known epoxy resin compositions tend to crack upon curing, so that the appearance of the moldings and coatings is impeded and semiconductor elements or devices become defective.
In order to solve the above problems, the present inventors have proposed epoxy resin composition having a high resistance to cracking in which block copolymers of aromatic polymers and organopolysiloxanes are added to curable epoxy resins (Japanese patent application Laid-Open No. 58-21417). However, there is a high demand for epoxy resin compositions which have a high resistance to cracking, a high glass transition point and a low coefficient of expansion, so that the degree of deformation upon molding is small with good moldability without sacrificing mechanical characteristics such as bending strength, a modulus of elasticity in flexure, mechanical strength and the like.
Japanese Patent Publication No. 49-49176, Japanese patent application Laid-Open No. 59-129252, Japanese patent application Laid-Open No. 60-69129 and Australian Pat. No. 235757 disclose epoxy resin compositions containing an organopolysiloxane.